Effect of Cerium Oxide Additions on the Densification Behaviour of Alumina Gels

1985 ◽  
Vol 60 ◽  
Author(s):  
Ratnesh Dwivedi ◽  
Jane Adams
Keyword(s):  
Cerium Oxide ◽  
Theoretical Density ◽  
Sintering Behavior ◽  
Growth Morphology ◽  
Pure Alumina ◽  
Densification Behaviour ◽  
Alumina Gel ◽  
Identical Manner ◽  
Alumina Gels ◽  
Alpha Alumina

AbstractSintering behavior of gel-derived alumina containing 2.8 mol percent cerium oxide (Ce2 O3) was studied at 1400°C. The growth morphology of alpha alumina in cerium oxide-containing aluminas was found to be significantly different form that of pure gel-derived alumina. Alumina gel containing 2.8 mol % Ce2 O3 was found to densify to 81% of the theoretical density as compared to 65% for pure alumina gels. The powdered cerium oxide-containing gels, pressed into a pellet, could be sintered to 97% of the theoretical density at 1400°C as compared to 87% found for pure alumina gel powder processed in an identical manner.

Microstructural Transformations in Alumina Gels

1984 ◽  
Vol 32 ◽  
Author(s):  
F. W. Dynys ◽  
M. Ljungberg ◽  
J. W. Halloran
Keyword(s):  
Phase Transformations ◽  
Microstructural Development ◽  
Transition Alumina ◽  
Hydrous Oxides ◽  
Alumina Gels ◽  
Alpha Alumina

ABSTRACTMicrostructural development in alumina gels is dominated by a series of phase transformations between the hydrous oxides to transition alumina phases, between transition phases, and transformation to alpha-alumina. These microstructural transformations are illustrated in boehmite AlOOH and bayerite Al(OH)3 gels.

Nucleation of alpha alumina in boehmite gel

1990 ◽  
Vol 5 (2) ◽  
pp. 278-285 ◽  
Author(s):  
Ladislav Pach ◽  
Rustum Roy ◽  
Sridhar Komarneni
Keyword(s):  
Parent Phase ◽  
Seed Surface ◽  
Nucleation Sites ◽  
Alumina Gel ◽  
Alpha Alumina ◽  
Transformation Enthalpy

Transformation of boehmitc-derived alumina gel to α–Al2O3 in unseeded gels is strongly influenced by the parent phase, θ-Al2O3. In seeded gels the perfect structure of the epitaxial substrate (α–Al2O3, 0.3 wt. %) influences the surrounding defect θ-phase resulting in (a) fewer imperfections due to lower transformation enthalpy to α–Al2O3, and (b) multiple nucleation sites of α–Al2O3 at the α–Al2O3 seed surface. The rate of transformation expressed for the same number of α–Al2O3 nuclei in unseeded and seeded gels indicates that it is faster in the unseeded gel than in the seeded gel.

The Sintering Mixed Powders Behavior of Triuranium Octoxide in Uranium Dioxide

2015 ◽  
Vol 1114 ◽  
pp. 22-28
Author(s):  
Aurica Barbu ◽  
Mihai Ovidiu Cojocaru
Keyword(s):  
Uranium Dioxide ◽  
Surface Defects ◽  
Hydrogen Atmosphere ◽  
Diameter Ratio ◽  
Theoretical Density ◽  
Metallographic Analysis ◽  
Sintering Behavior ◽  
Cold Pressing ◽  
Triuranium Octoxide

The main aim of this research was to study the sintering behavior in hydrogen atmosphere of mixed powders of triuranium octoxide (U3O8) powder in dioxide uranium (UO2) powders. By cold pressing the green pellets of mixed powders of triuranium octoxide in hyper stoichiometric uranium dioxide has density over 40 % UO2 theoretical density (TD). The sintered pellets had a height diameter ratio (H / D) over one and oxygen uranium ratio (O/U) near stoichiometry of uranium dioxide (UO2). The densities of sintered pellets were up to 97% of uranium dioxide theoretical density. The proposed treatment of sintering are function of green pellets density. Increasing the proportion of triuranium octoxide leads to a decrease in the density of the sinter pellets. The pellets made by 100 % of triuranium octoxide not resist to proposed sintering treatment. The metallographic analysis show uniform grains for sinter pellets made by the 30 % mixture of triuranium octoxide in uranium dioxide. This UO2 sinter pellets are without surface defects.

Sintering Behavior of AL2O3 Ceramics Doped with Pre-Sintered NB2O5 and LiF

2020 ◽  
Vol 1012 ◽  
pp. 190-195
Author(s):  
Pedro Henrique Poubel Mendonça da Silveira ◽  
Paulo Roberto Rodrigues de Jesus ◽  
Matheus Pereira Ribeiro ◽  
Sergio Neves Monteiro ◽  
Julio César Soares De Oliveira ◽  
...  
Keyword(s):  
Grain Size ◽  
Theoretical Density ◽  
Sintering Behavior ◽  
Different Temperatures

A study was carried out on the behavior during the sintering of Al2O3 ceramics with pre-sintering of the additives Nb2O5 and LiF at different temperatures. It was observed through XRD and DSC the formation of the LiNb3O8, Nb3O7F and LiNbO3 phases during the pre-sintering of the additive powders and the formation of the LiAl5O8, AlNbO4 phases during the sintering of the samples The samples showed densities around 91% of the theoretical density, and pre-sintered samples showed low growth in grain size.

Effect of redox reaction on the sintering behavior of cerium oxide

1997 ◽  
Vol 45 (9) ◽  
pp. 3635-3639 ◽  
Author(s):  
Yanchun Zhou ◽  
Mohamed N. Rahaman
Keyword(s):  
Cerium Oxide ◽  
Redox Reaction ◽  
Sintering Behavior

Low-Temperature Sintering of ZnO–TiO2 Ceramics

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Zhengwei Nie ◽  
Yuyi Lin ◽  
Feixue Wang
Keyword(s):  
Low Temperature ◽  
Vanadium Pentoxide ◽  
Material Properties ◽  
Sintering Temperature ◽  
Theoretical Density ◽  
Sintering Behavior ◽  
Low Temperature Sintering ◽  
Sintering Aid

Vanadium pentoxide (V2O5) was chosen as a sintering aid to lower the sintering temperature of the ZnO–TiO2 system. The effect of V2O5 on the sintering behavior and material properties of ZnO–TiO2 ceramics and cermets made of ZnO–TiO2 ceramics and copper (Cu) was investigated as a function of V2O5 percentage and sintering temperature. Densities and hardness of the specimens were improved with an increase of V2O5 up to 2 wt. %. The sintering temperature of the specimens can be reduced to below 1000 °C. The properties of ZnO–TiO2 ceramics and cermets made from ZnO–TiO2 ceramics and Cu with V2O5 are strongly dependent on the sintering temperature. The density of ZnO–TiO2 ceramics and cermets was increased up to 95%, 90% of theoretical density at 900–920 °C, 960–1000 °C, respectively, for 4 hrs.

scholarly journals Titania Effect on Sintering behavior of Alumina

2009 ◽  
Vol 6 (4) ◽  
pp. 770-774
Author(s):  
Baghdad Science Journal
Keyword(s):  
Water Absorption ◽  
Thermal Shock ◽  
Thermal Shock Resistance ◽  
Sintering Temperature ◽  
Shrinkage Porosity ◽  
Sintering Behavior ◽  
Pure Alumina ◽  
Titania Powder ◽  
Laboratory Results ◽  
Shock Resistance

The sintering behavior of Alumina was investigated by adding TiO2. The addition of TiO2 lowered the sintering temperature of the Alumina compared with those of pure Alumina. The result suggests that TiO2 acts as an activator for sintering of Alumina. Water absorption, apparent porosity and density were examined for both pure and TiO2 added to Alumina samples. The variations of sintering behavior were discussed in terms of shrinkage, porosity, water absorption and density. Thermal shock resistance was also examined. In term of this work, the way of improving the thermal shock resistance in oxide- based materials by adding reactive Titania powder to the Alumina samples. The laboratory results showed an improvement in thermal shock resistance property of the products which open the horizon of development of the final products.

Preparation of Al2O3 Coated SiC Powders by Heterogeneous Precipitation

2010 ◽  
Author(s):  
Dan Zhang ◽  
Jinping Suo
Keyword(s):  
Raw Material ◽  
Precipitation Method ◽  
Phase Transformation Temperature ◽  
X Ray Diffraction ◽  
Pure Alumina ◽  
Heterogeneous Precipitation ◽  
Surface Active ◽  
Tritium Permeation ◽  
Α Al2o3 ◽  
Alpha Alumina

Alumina has been identified as a most promising material in tritium permeation barrier. By introducing some additive into the alumina improves its effectiveness. The purpose of this study was to synthesize Al2O3 coated SiC particles by heterogeneous precipitation method to replace the pure alumina as the raw material of coating. A series of factors which influenced the properties of coated powders had been studied, including the concentration of Al(NO3)3 solution, surface active reagent, the addition amount of SiC, calcinations temperature etc. The coated powders were analyzed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Zeta-potential analyzer. The result indicates that the addition of certain amount of nano powers can reduce the phase transformation temperature of the alpha alumina. α-Al2O3 coated SiC powders were obtained by calcining Al(OH)3/SiC precursor at 1100 degree centigrade.

Phase Transformation and Densification of Nanostructured Alumina. Effect of Seeding and Doping

2005 ◽  
Vol 237-240 ◽  
pp. 665-670 ◽  
Author(s):  
Corinne Legros ◽  
Claude Carry ◽  
Sylvie Lartigue-Korinek ◽  
Paul Bowen
Keyword(s):  
Phase Transformation ◽  
Microstructural Evolution ◽  
Nucleation Rate ◽  
Short Range ◽  
Alpha Phase ◽  
Densification Behaviour ◽  
Kinetics Of ◽  
Alpha Alumina

By following the densification kinetics of nanocrystalline g alumina and corresponding microstructural evolution we showed that the diffusive transformation gamma-alpha involves several processes such as nucleation of alpha phase, rearrangement of gamma crystallite at alpha seed and grain surfaces, formation of porous alpha alumina monocrystalline colonies. Results concerning the effects of seeding and doping elements on the transformation-densification behaviour of the same g-alumina raw powder batch are also presented. Doping elements seem to have no influence on nucleation rate but could modify the redistribution rate of the ions during the transformation by short range diffusion of doping elements.

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